This section provides background information related to the present disclosure which is not necessarily prior art.
In an attempt to reduce the quantity of NOx and particulate matter emitted to the atmosphere during internal combustion engine operation, a number of exhaust aftertreatment or emission control devices (“exhaust treatment devices”) have been developed. A need for exhaust aftertreatment systems particularly arises when diesel combustion processes are implemented. Typical aftertreatment systems for diesel engine exhaust may include a hydrocarbon (HC) injector, a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a selective catalytic reduction (SCR) system (including a urea injector).
Exhaust treatment systems may include insulation to retain heat within the exhaust treatment devices or for shielding temperature-sensitive components or materials that are located nearby. The insulation may be disposed between two walls. An inner wall defines a passage for exhaust gas flow and an outer wall retains the insulation and protects it from the environment.